gfx/layers/apz/src/RecentEventsBuffer.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_layers_RecentEventsBuffer_h
   8 #define mozilla_layers_RecentEventsBuffer_h
   9
  10 #include <deque>
  11
  12 #include "mozilla/TimeStamp.h"
  13
  14 namespace mozilla {
  15 namespace layers {
  16 /**
  17  * RecentEventsBuffer: maintains an age constrained buffer of events
  18  *
  19  * Intended for use with elements of type InputData, but the only requirement
  20  * is a member "mTimeStamp" of type TimeStamp
  21  */
  22 template <typename Event>
  23 class RecentEventsBuffer {
  24  public:
  25   explicit RecentEventsBuffer(TimeDuration maxAge);
  26
  27   void push(Event event);
  28   void clear();
  29
  30   typedef typename std::deque<Event>::size_type size_type;
  31   size_type size() { return mBuffer.size(); }
  32
  33   // Delegate to container for iterators
  34   typedef typename std::deque<Event>::iterator iterator;
  35   typedef typename std::deque<Event>::const_iterator const_iterator;
  36   iterator begin() { return mBuffer.begin(); }
  37   iterator end() { return mBuffer.end(); }
  38   const_iterator cbegin() const { return mBuffer.cbegin(); }
  39   const_iterator cend() const { return mBuffer.cend(); }
  40
  41   // Also delegate for front/back
  42   typedef typename std::deque<Event>::reference reference;
  43   typedef typename std::deque<Event>::const_reference const_reference;
  44   reference front() { return mBuffer.front(); }
  45   reference back() { return mBuffer.back(); }
  46   const_reference front() const { return mBuffer.front(); }
  47   const_reference back() const { return mBuffer.back(); }
  48
  49  private:
  50   TimeDuration mMaxAge;
  51   std::deque<Event> mBuffer;
  52 };
  53
  54 template <typename Event>
  55 RecentEventsBuffer<Event>::RecentEventsBuffer(TimeDuration maxAge)
  56     : mMaxAge(maxAge), mBuffer() {}
  57
  58 template <typename Event>
  59 void RecentEventsBuffer<Event>::push(Event event) {
  60   // Events must be pushed in chronological order
  61   MOZ_ASSERT(mBuffer.empty() || mBuffer.back().mTimeStamp <= event.mTimeStamp);
  62
  63   mBuffer.push_back(event);
  64
  65   // Flush all events older than the given lifetime
  66   TimeStamp bound = event.mTimeStamp - mMaxAge;
  67   while (!mBuffer.empty()) {
  68     if (mBuffer.front().mTimeStamp >= bound) {
  69       break;
  70     }
  71     mBuffer.pop_front();
  72   }
  73 }
  74
  75 template <typename Event>
  76 void RecentEventsBuffer<Event>::clear() {
  77   mBuffer.clear();
  78 }
  79
  80 }  // namespace layers
  81 }  // namespace mozilla
  82
  83 #endif  // mozilla_layers_RecentEventsBuffer_h